This invention relates to a novel chelate polymer, and more particularly to a polymaleimide type chelate polymer capable of changing chromaticity distinctly with pH and to a method for the manufacture of the chelate polymer. Many substances have heretofore been known to serve effectively as pH indicators and metal indicators. These substances change color at specific pH values or react with metal ions to form corresponding metal chelates and assume peculiar hues. Owing to this property, they are extensively used as in microchemicalanalysis, for example.
The inventors earlier proposed poly-2-(2'-thiazolylazo)-4-vinylphenols which they found to react catalytically with a wide variety of metals such as, for example, copper, nickel, zinc, cadmium, mercury, uranium, cobalt, iron, and palladium and produce corresponding chelates and, therefore, serve as metal indicators having pronounced color differences.
With a view to exploiting the chelating property of 2-thiazolylazo type substances, the inventors prepared chelate polymers by incorporating these substances into various polymers and studied their properties. They have consequently found that polymaleimide type chelate polymers selectively form chelates with specific metals, namely copper, nickel, cobalt and palladium, with pronounced differences in color. They have further found that the polymaleimide type chelate polymers according to this invention by themselves manifest pronounced color differences with change in pH and, therefore, are highly useful as pH indicators and that their changes in color proceed reversibly and with consistent coloration with repeated changes in pH. It has also been ascertained that the chelate polymers of the present invention produce a plurality of changes in color with pH particularly in the range of acidity and, therefore, serve advantageously as pH indicators in a wide variety of applications.
An object of this invention is to provide novel chelate polymers which selectively react with specific metals, i.e. copper, nickel, cobalt, and palladium to form chelates of specific colors and, therefore, serve advantageously as metal indicators.
Another object of this invention is to provide novel polymers which change color reversibly and with a pronounced color difference with pH and, therefore, prove to be highly useful as pH indicators.
A further object of this invention is to provide a method for the manufacture of the novel polymers mentioned above.
The other objects and characteristics of the present invention will become apparent from the further disclosure of the invention to be made hereinbelow with reference to the accompanying drawing.